Control system for electron discharge devices



vOct. 30, 1934. J. L. FINCH 1,978,706

CONTROL SYSTEM FOR ELECTRON DISCHARGE DEVICES Filed Sept. 8, 1930INVENTOR JAMES L FiNCH BY WWW ATTORNEY Patented Oct. 30, 19 34 PATENTOFFICE CONTROL SYSTEM Foa ELECTRON DISCHARGE DEVICES James L. Finch,Patchogne, N. Y.,

BadioCO Delaware assignor to rporation of America, a corporation ofApplication September 8, 1930, Serial No. 480,445

This invention relates to a control system for controlling the flow ofcurrent in a system of circuits and especially to one wherein a gasfilled t'riode is used to control the flow of alternating I currents.

Heretofore, systems have been devised wherein contacts pass or cut of!the flow of current through circuits of a system. Because of the factthat it is sometimes impossible to employ contacts sufliciently large tohandle large amounts of power or to control them with suincientprecision, the amount of power that can be provided by this system islimited. In order to use the same contacts and increase the power 18under control, the contacts are sometimes placed .in the control windingcircuit of an electromagnetic relay, and sometimes in the controlelectrode ,circuit of an electron discharge device whose anode circuitcontrols an electromagnetic relay. The relay in turn turns on or off,for example, heating current. However, the latter systems have thedisadvantages of being complicated and relativeLv expensive.

A prime desideratum is the removal of the foregoing difllculties; and,to do so it is an object of this invention to provide a system whereincontacts, when open, allow the flow of a consid erable amount of workingcurrent or power and, when closed, remove the working current or '80power.

It is a further object of this invention to provide, to act inconjunction with the contacts, an electron discharge device arrangementhaving a working element in-its anode circuit the 86 current throughwhich is turned completely on or oil by action of the contactsassociated therewith. I

Peculiarly adapted for this purpose is the thyratron tube which is anelectron discharge device having a disc like anode, a control electrode,a cathode, and, a certain amount of mercury vapor within its container.A negative potential on the control electrode of such a tube iseffective in preventing anode current flow 46 .despite high anodepotentials, but, once anode current flow has been started high negativepotentials upon the control electrode or grid are alone ineffective tostop anode current flow. Cessation of anode current can be effectedsolely so by a reduction in anode potential.

As required by statute the present invention is defined in the appendedclaim. However, it may be best understood both as to its structuralorganization and mode of operation by referring ,56 to the accomp nyingdrawing. wherein,

1 Claim. (01. 219-20) Figure '1 illustrates a heating system utilizing asingle electron discharge device, pulsations of current flowing througha heating element from an alternating source in response to action ofcontacts opening and closing a control circuit, 59 and,

Figure 2 illustrates a heating system wherein by the use of a pluralityof electron discharge devices, a substantially unidirectional currentflows through a heating circuit from an alternating current source inaccordance with action of operated contacts in a control circuit foropening and closing the same.

Referring to Figure l, alternating heating energy is supplied to anelectron discharge device, 7 such as a thyratron, from an energy inputcircult 2 through a primary 4 of a transformer 6 having as shown, asplit secondary 8. Heating energy is taken from a portion of the.secondary winding 8 through conductors 10 to the cathode 7 12 ofelectron discharge device 14. To establish an electrical balance, aconductor 16 is connected from the primary winding 4 of transformer 6 tothe midpoint of potentiometer 18 connected across cathode 12.

A control circuit, formed by the secondary winding of. transformer 6,temperature responsive contacts 20 and impedance 22 preferably in theform of a high resistance is connected across the input terminals of theelectron discharge device 14.

The output circuit of electron discharge device 14, comprising a heatingor working element in the form of a resistance 24 is used for thepurpose of maintaining a compartment and the apparatus therein, (notshown) at a constant temperature. Anode potential is supplied to theanode 26 of the electron discharge device 14 through heating element 24and conductor 28 leading to the primary winding 4 of transformer 8.

The control electrode 30, of electron discharge device 14, with contacts20, open, is supplied with alternating potentials from the secondary 8of transformer 6 in phase with the potentials supplied to the anode 26.Consequently, during alternating half cycles of the input energy, whenanode 26 and grid 30 are rendered positive, working current pulsationswill flow in the output circuit increasing the temperature of thecompartment about and for apparatus close to resistance element 24.

Upon reaching a desired temperature, contacts 20, which also are inclose proximity to the elements to be maintained at constant tem- 9perature, will close as a result of which, the potentials applied to thecontrol electrode 30 are efiectively reversed in phase, since theenergization of the control circuit with the contacts closed is suchthat current flowing through high resistance 22 will engender potentialson control electrode 30 out of phase with those on the anode 26.Therefore, no longer will there be anode current flow and consequently,heating action, until the ambient temperature of contacts 20 drops to avalue such that contacts 20 open thereby allowing of the in phasepotential excitation of anode 26 and control electrode 30.

"in order to. increase the energy output, a plurality of tubes such astube 14, may be paralleled, similar electrodes being paralleledtogether.

The circuit, moreover, may not only be used in connection with atemperature controlled system, but, contacts 20 may be opened and closedin any desired fashion, for example, in response to fluid flow, in whichcase the voltage drop across the element 24 may be utilized for thepurpose of controlling apparatus to control the fluid flow in desiredfashion.

In order to make the output or working energy flow more nearlycontinuously, as well as to increase the same, the arrangement shown inFigure 2 may be used to good advantage. Electron discharge devices 32,34 have their anodes connected serially through secondary winding 36 oftransformer 38 supplied with energy from a suitable energy input circuit40. The cathodes of devices 32, 34 are connected together and energizedin any suitable fashion such as by an energizing transformer 42.

The control electrodes of the tubes are connected together throughimpedances 44, 46 preferably resistances. The anode circuit is completedfrom the midpoint of secondary 36 through conductor 48, element 50 tothe midpoint of the secondary of transformer '42, which is at a zeroalternating current potential point.

The control circuit 52 is connected across the impedances 44, 46 suchthat with contacts 54 closed, the alternating potentials applied to -thecontrol electrodes or grids and anodes or plates. of each of the tubes32, 34 are out of phase. With contacts 54 open, the potentials appliedto the grid and plate of each tube are in phase allowing current flowtherethrough. Consequently, it should be clear that with contacts 54open, representing a cold condition, rectification of input energy frominput circuit 40 will occur and current will flow in the output orworking circuit, or, through heating element 50.

Upon reaching a desired, predetermined temperature, the temperatureresponsive contacts 54 will'close, as a result of which energy fed fromsource 40 into the secondary 56 of transformer 38 will cause potentialvariations across impedances 44, 46 such that the control electrodes ofthe tubes will shift in potential 180 degrees out of phase with thepotentials on their cooperating anodes. Current flow through the heatingelement 50 will consequently cease.

Asstated in connection with Figure 1, the tubes 32, 34 may be paralleledby suitable similar tubes in order to increase the output, contacts 54may be actuated in any desired fashion, and, the current flow throughresistance 50 may be utilized in any desired fashion rather than solelyfor heating purposes.

Having thus described my invention, what I claim is:

Temperature control apparatus having, in combination, a pair of gasfilled electron glow discharge devices, each having anode, cathode andcontrol electrodes, a first transformer having a single primary windingand two secondary windings, a source of alternating potential acrosssaid primary winding, the anodes of both said devices being seriallycoupled through one of said secondary windings, the control electrodesof said devices being coupled through two serially arranged highresistances, means for heating the cathodes of said devices comprising asource of potential coupled to said cathodes through a secondtransfofiner the secondary of which is coupled across said cathodes inparallel, a connection including a serially arranged heater circuit froma point intermediate the ends of said one secondary winding of saidfirst transformer to said cathodes, and a connection from a pointintermediate said two high resistances to said cathodes, a pair ofcontacts thermostatically controlled, one of said contactsbeingflconnected to one of said control electrodes and the other of saidcontacts being connected to one side of said other secondary winding ofsaid first transformer, the other side of said last secondary windingbeing connected to said other control electrode whereby potentialsapplied to said control electrodes are in phase with potentials appliedto said anodes when said contacts are open and out of phase when saidcontacts are closed.

JAMES L. FINCH.

